Cron expression `* 12 21 MAR *` runs every minute, between 12:00 and 12:59, on day 21 of the month, only in March

Read more in the dedicated guide: Cron every minute.

What this cron means, field by field

Each field of * 12 21 MAR * controls one dimension of the schedule. Hover over any value in the editor above to see its tooltip; the table below summarises the same information.

Field	Value	Means	Range / hint
minute	`*`	every value (wildcard)	0-59. The minute(s) of the hour the job will fire.
hour	`12`	at hour 12	0-23. The hour(s) of the day the job will fire (0 = midnight, 23 = 11 PM).
day of month	`21`	at day of month 21	1-31. The day(s) of the month. Use * if you want every day.
month	`MAR`	at month MAR	1-12 or JAN-DEC. The month(s). Use * for every month.
day of week	`*`	every value (wildcard)	0-7 or SUN-SAT (0 and 7 both mean Sunday). Use * for every day of the week.

Next 5 runs

Shown in UTC. Change the timezone in the editor.

Next runs · UTC

Sun 21 Mar · 12:00in 185d 14h
Sun 21 Mar · 12:01
Sun 21 Mar · 12:02
Sun 21 Mar · 12:03
Sun 21 Mar · 12:04

Similar cron expressions

Common variations and tweaks of * 12 21 MAR *.

Where else this cron could be used

The same expression * 12 21 MAR * works in:

Standard Unix crontab (5-field syntax).
AWS EventBridge / Lambda Scheduled (with a 6th field for year, often *).
Vercel cron jobs (declared in vercel.json).
Quartz Scheduler and node-cron, robfig/cron and similar libraries.

Examples

0 18 * * *
Every day at 18:00
0 */5 * * *
Every 5 hours
0 18 * * 1-5
Weekdays at 18:00
0 0 1 * *
Once a month, on the 1st at midnight

Cheatsheet

Full cheatsheet

Field	Req.	Range	Wildcards
minute	yes	0-59	, - * /
hour	yes	0-23	, - * /
day of month	yes	1-31	, - * /
month	yes	1-12 or JAN-DEC	, - * /
day of week	yes	0-6 or names; some dialects use 0-7 or 1-7 — see Dialects	, - * /

Frequently asked questions

What does the cron expression `* 12 21 MAR *` mean?

every minute, between 12:00 and 12:59, on day 21 of the month, only in March.

When does `* 12 21 MAR *` run next?

The next runs (UTC): 2027-03-21 12:00; 2027-03-21 12:01; 2027-03-21 12:02; 2027-03-21 12:03; 2027-03-21 12:04.

Is `* 12 21 MAR *` a valid cron expression?

Yes - CronTool's parser accepts this expression and the calendar projects future runs successfully.